FIG. 1 shows a known electromagnetically operated fuel injector 2 that is particularly suited to use within diesel engines. The injector 2 is generally elongate in form and includes a nozzle holder body 4 at its upper end that is connected to an injection nozzle arrangement 6 at its lower end, in the orientation shown.
The injection nozzle arrangement 6 comprises three components that are housed within a cap nut 8 that is approximately U-shaped in cross section and which engages the nozzle holder body 4 by way of a screw thread at its more open end, thereby securing the injection nozzle arrangement 6 to the nozzle holder body 4.
The first component of the injection nozzle arrangement 6 is an elongated injection nozzle 10 having a tip end 12 that extends through an aperture 14 formed in the base of the cap nut 8. The injection nozzle 10 houses a spring biased injection needle 16 that is slidable within the injection nozzle 10 so as to control the delivery of fuel through a set of nozzle holes (not shown), in use.
A first distance piece 18 lies above the injection nozzle 10 (in the orientation shown in FIG. 1) and includes a through-drilling 20 that serves to convey pressurised fuel from a valve block 22 located adjacent and above the distance piece 18 to the injection nozzle 10. The distance piece 18 also includes a centrally disposed blind bore 24 which receives a back end of the injection needle 16 such that a control chamber 26 is defined between the injection needle 16 and the blind end of the bore 24.
The valve block 22 is positioned intermediate the distance piece 18 and the nozzle holder body 4 and includes a high pressure drilling 28 that conveys fuel from a high pressure inlet drilling 30 defined in the nozzle holder body 4 to the drilling 20 in the distance piece 18. The valve block 22 also includes a valve arrangement 32 comprising an elongate valve pin 34 and a disc-shaped armature 36 attached thereto.
The armature 36 is acted on by a electromagnetic actuator 38 that is received within a recess 40 defined in the underside of the nozzle holder body 4. Depending on the activation state of the actuator 38, the armature 36 is raised or lowered which causes the valve member 34 to engage or disengage alternately each of two respective valve seatings 42 and 43 to control the pressure of fuel within the control chamber 26.
An upper region 44 of the nozzle holder body 4 includes a lateral recess 46 which receives an electrical connector 48. A longitudinal bore 50 extends from the lateral recess 46 to the actuator recess 40. An electrical supply lead 52 (with at least two cores) extends through the longitudinal bore 50 from the electrical connector 48 to an upper face 53 of the actuator and connects thereto thereby supplying electrical energy to the actuator. It should be appreciated that the precise structural details of how the actuator 38 connects to the electrical supply lead 52 are not described.
The nozzle holder body 4 further includes a high pressure fuel inlet 54 which is defined by a transversely extending port approximately in the mid-region of the nozzle holder body 4. The fuel inlet 54 defines a conical seating surface which is shaped for engagement with a high pressure fuel supply connector (not shown), in use. An oblique drilling 56 extends from the inlet 54 into the nozzle holder body 4 and then angles downward via drilling 30 in a direction to connect to the high pressure drilling 28 defined in the valve block 22.
There is pressure on Fuel Injection Equipment (FIE) manufacturers to make FIE for engines which are smaller, lighter and more economical, including injectors of a smaller diameter. Therefore, there is a need to reduce the space efficiency and overall size of engine components such as the known fuel injector 2 as described above with reference to FIG. 1.